A Sensitive and Selective Method for Determination of Aesculin in Cortex Fraxini by Liquid Chromatography Quadrupole Time-of-Flight Tandem Mass Spectrometry and Application in Pharmacokinetic Study
A rapid and sensitive method for determining aesculin of Cortex fraxini in rat was developed using high-performance liquid chromatography (HPLC) quadrupole time-of-flight (QTOF) tandem mass (MS/MS). Rat plasma was pretreated by fourfold methanol to remove plasma proteins. Chromatographic separation was performed on a reverse phase column. A tandem mass spectrometric detection with an electrospray ionization (ESI) interface was achieved using collision-induced dissociation (CID) under positive ionization mode. The MS/MS patterns monitored were m/z 341.2716 → m/z 179.1043 for aesculin and m/z 248.3025 → m/z 120.9130 for tinidazole (internal standard). The linear range was calculated to be 10.0–1500.0？ng/mL with a detection limit of 2.0？ng/mL. The inter- and intraday accuracy and precision were within ±7.0%. Pharmacokinetic study showed that aesculin was confirmed to be a one-compartment open model. The method is believed to have good linear range, high sensitivity and recoveries, and superior analytical efficiency. It will probably be an alternative for pharmacokinetic study of aesculin. 1. Introduction Cortex fraxini, named “Qin Pi” in China, is the dry barks of Oleaceae plant Fraxinus rhynchophylla Hance, F. rhynchophylla Hance, or Fraxinus paxiana [1]. Cortex fraxini is confirmed to inhibit the growth of dysentery bacillus and staphylococcus [2] as well as have diuretic, anticoagulant, antiallergic, and antioxidant effects [3–5]. As a favorite and largely used medicinal plant in traditional Chinese practice, it is the main herb in a formula frequently prescribed for fighting diseases including bacterial enteritis, acute or chronic enteritis, acute nephritis, and ulcerous coloitis [6]. Aesculin is described as a marker for estimating quality of Cortex fraxini in Chinese pharmacopeia due to inhibiting xanthine oxidase and having antioxidant activity and antitumor activity [7, 8]. The methodologies on the basis of the tandem of HPLC-DAD-MS [9, 10] and capillary electrophoresis [11–14] have been widely used to quantify the amount of aesculin in this plant and its preparations. Ultraviolet absorption spectrum has also been used in the measuring of aesculin in Cortex fraxini through artificial neural network [15]. In addition, a high-performance liquid chromatographic method was established for pharmacokinetic study of aesculin in a previous report [16]. Recently, a method using high performance liquid chromatography with fluorescent detection has been developed for monitoring aesculin in rabbit plasma [17]. These assays have a potential to be officially
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